Methods for producing textured electrode based energy storage device

ABSTRACT

This method enables the use of nanowire or nano-textured forms of Polyaniline and other conductive polymers in energy storage components. The delicate nature of these very high surface area materials are preserved during the continuous electrochemical synthesis, drying, solvent application and physical assembly. The invention also relates to a negative electrode that is comprised of etched, lithiated aluminum that is safer and lighter weight than conventional carbon based lithium-ion negative electrodes. The invention provides for improved methods for making negative and positive electrodes and for energy storage devices containing them. The invention provides sufficient stability in organic solvent and electrolyte solutions, where the prior art processes commonly fail. The invention further provides stability during repetitive charge and discharge. The invention also provides for novel microstructure protecting support membranes to be used in an energy storage device.

RELATED APPLICATIONS

This application is a divisional of U.S. application Ser. No.13/018,586, filed Feb. 1, 2011, which is a continuation of InternationalApplication No. PCT/US10/58418, which designated the United States andwas filed on Nov. 30, 2010, published in English, which claims thebenefit of U.S. Provisional Application No. 61/265,167, filed Nov. 30,2009 and U.S. Provisional Application No. 61/353,500, filed Jun. 10,2010. The entire teachings of the above applications are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

In 1986, Alan MacDiamid won a Nobel Prize for his work in conductivepolymers. In his U.S. Pat. No. 4,940,640, MacDiamid disclosed thechemical nature of polyaniline and the five possible states ofoxidation. At that time, polyaniline was synthesized by chemical routes,and later stimulated into various electrical states by electrochemistry.In the early 1990's, researchers such as V. Gupta and M. Pasquali,published the construction of polyaniline and polypyrrole conductivenanowires by electrochemical synthesis in acids such as Hydrochloric,Sulphuric and Perchloric acids. These films had very high electrolyticperformance, but were fairly unstable physically and electrically,decomposing in use. Over the years since then, gradual increases inchemical stability have been achieved by including dopant donors such assulphonic acid. In this case, the RSO₃ ⁻ anion is synthesized into thepolyaniline, creating a more stable material, albeit at the expense ofslower growth or poorer adhesion at the electrode. Since the initialwork, many papers have been published regarding electrochemical andchemical synthesis; however, there has been a distinct lack ofimplementation of the most useful forms of conductive polymers due tothe delicate nature of “brush” like features. The loose fibers ornano-texture can mat down during assembly to the opposing electrode,reducing most of the useful surface area. The current collectors for thestudies have been primarily noble metals, which are costly andtherefore, limiting to commercial applications. Lack of adhesion toother less noble metals primarily due to oxidation has also limitedtheir use. Commercial applications of conductive polymers have thereforebeen via the bulk chemical (granular) synthesis route, where theavailable specific surface areas are as much as ten times less ascompared to the more delicate electrochemically grown nano-texture.

Therefore, it is an object of the present invention to provide a methodfor producing nano-textured conductive polymers on non-noble metalelectrodes wherein the delicate nature of these very high surface areamaterials is preserved during the continuous electrochemical synthesis,drying, solvent application and physical assembly and repetitive chargeand discharge.

SUMMARY OF THE INVENTION

The invention relates to the synthesis of a conductive polymer onto anon-noble metal electrode. High power and high energy organic nanowireultracapacitors (supercapacitors) or batteries are made from low-costmaterials, and produced by an automated continuous sheet process. Thecontinuous method of manufacture includes electrochemical techniques:One technique is especially adapted to initiate a favorable seed layeror template for growth of the conductive polymer that has good adhesionand electrical properties; another technique provides rapid growth uponthe seed layer or template while propagating favorable morphology andelectrical properties. The invention also relates to a negativeelectrode that is comprised of etched, lithiated aluminum that is saferand lighter weight than conventional carbon based lithium-ion negativeelectrodes. The invention provides for improved methods for makingnegative and positive electrodes and for energy storage devicescontaining them. The invention provides sufficient stability in organicsolvent and electrolyte solutions, where the prior art processescommonly fail. The invention further provides stability duringrepetitive charge and discharge. The invention also provides for novelmicrostructure protecting support membranes to be used in an energystorage device.

BRIEF DESCRIPTION OF THE DRAWINGS

The foregoing and other objects, features and advantages of theinvention will be apparent from the following more particulardescription of preferred embodiments of the invention, as illustrated inthe accompanying drawings in which like reference characters refer tothe same parts throughout the different views. The drawings are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention.

FIG. 1: Metal ribbon.

FIG. 2: Electrode layered structure.

FIG. 3: Electrochemical synthesis bath.

FIG. 4: Electron micrograph image of nanowire product.

FIG. 5: CV cycle testing of nanowire electrode.

FIG. 6: Manufacturing scheme.

FIGS. 7A-7C: Spacer/layer positive and negative electrodes.

FIGS. 8A-8C: Stack of alternating electrode and spacer layers.

FIG. 9: Ultracapacitor performance as a function of pH and dopant level.

FIGS. 10A and 10B: Discharge curves.

FIG. 11: Discharge curve at constant current of 2.5 mA/cm².

FIG. 12: Thermal model, showing adequacy of 4 micron substratethickness.

FIG. 13: Cycle testing of polyaniline on a base metal electrode.

FIG. 14: Illustrates performance of a half cell arrangement ofpolyaniline electrochemically synthesized onto graphite scrubbedAluminum 1145.

FIG. 15: Illustration of cyclic voltammetry of a Ni/4-APA/PANielectrode, as made in Example 1, response in aqueous low pH solutions.

FIGS. 16 and 17: Illustration of cyclic voltammetry of a Ni/C/PANielectrode, as made in Example 2, response of a 20 C film in aqueous lowpH solutions and nonaqueous solutions.

FIG. 18: Illustration of nonaqueous discharge capacity (mAh) for aNi/C/PANi electrode as a function of total Coulombs of aqueous growth.

FIG. 19: Illustration of a guide roller of the invention with a filmpulled over it. The line of tension is illustrated together with thepreferred fluid gap.

FIG. 20: Illustration of a perforated roller that can be used tominimize shear forces during processing.

FIG. 21: Illustrates an assembly wherein 5 layers of electrode plates (3per layer) are assembled with guide rollers for directing a film to eachlayer.

FIG. 22: Illustrates a preferred drying tunnel of the invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention relates to improved electrodes comprising a support,linker layer, and conductive polymers on one, two or more sides of thesupport as shown in FIG. 2. The electrode can preferably be in the shapeof a conductive ribbon or similar sheet having conductive polymer onboth sides. The methods of the invention can be used to make theimproved electrodes continuously or semi-continuously, as desired, andallow for electrode creation via chemical and electrochemical processsteps which can be applied simultaneously to both sides of thesubstrate.

The invention also relates to an innovation in chemistry, whereby theincorporation of high energy density (high surface morphology),successful synthesis on commodity metals, and successful transfer toorganic electrolytes allows for low cost, high density energy storage.

The invention further relates to improved energy storage manufacturing.The fundamental innovation in energy storage manufacturing is theability to synthesize nano-textured material in a continuous,non-contact process. The non-contact electrochemical synthesis allowsthe use of exceptionally thin substrates due to the low forces andtensions required by the non-contact process. The use of such thinsubstrates in turn lends itself to optimization through stacked designas a means of minimizing electrical path length and correspondingresistance. Low cost and high specific energy are achieved by using verysmall amounts of lightweight, commodity-priced metals.

The electrode comprises a support, a linker or bifunctional agent and aconductive polymer having a very high surface area. The electrode can beany shape or size. However, the electrode is preferably a thin sheet orplate. Ribbons of thin electrode, where the length far exceeds thewidth, are particularly preferred as they facilitate an efficientcontinuous processing. In this embodiment, the width is selected tocorrelate to the width of the finished product. The ribbon can then beeasily cut to the length of the finished product for final assembly.FIG. 1 illustrates such a ribbon. The embodiment in FIG. 1 showsoptional sprocket holes along the length of the ribbon.

The support should be sufficiently thick as to provide meaningfulsupport and durability to the device, thereby protecting the polymerstructure from physical stresses which can be caused by bending andflexing. However, the support should not be so thick as to be unjustlyheavy for the contemplated use. In many applications, the thickness ofthe support can be less than about 100 microns, preferably less thanabout 50 microns and more preferably less about 10 microns. Further, thesupport can generally be greater than about 4 microns.

The support can be made of a large variety of materials. It isunderstood that the support comprises a conductive material or metal. Inan alternative embodiment, the conductive material can coat a substrate(which need not be conductive), such as polymers, plastics, cellulosicmaterials, resins, glass, ceramics, metals, graphite and the like. Apolymeric support can be a polyester, such as polyethyleneterephthalate, PET.

The electrode can be made of, contain or be coated with a conductivemetal, e.g. Titanium, Aluminum, Nickel, Stainless Steel, Tin, Gold, andPlatinum. Non-noble metals are preferred due to their lower cost.Aluminum is preferred because of its low cost and availability. Nickelis preferred due to its low cost and relative chemical stability of itssurface.

In this example, the thickness of the metal is about 2000 Angstromsthick each side on a 4 micron or greater thick polymer sheet such aspolyester. Other polymers such as treated BOPP (biaxially orientedpolypropylene) can be used, but polyesters have good to excellentnatural adhesion properties with regard to evaporated metals. Sprocketholes can be incorporated along one or both lengths of the ribbon tofacilitate transport through the process.

In one embodiment of the invention, the process includes deposition ofan evaporated conductive metal on a substrate or an electroplating stepto produce the support. Such processes are well known in the art.Preferably, thin films or foils of conductive materials are preferred.

In a preferred embodiment of the invention, a conductive and exfoliable(sheets can be rubbed off by friction) form of carbon such as graphiteor graphene (cgg) is scrubbed, or buffed, onto the surface of theelectrode substrate or base metal electrode base. The exfoliable carbonbecomes imbedded in the electrode substrate and provides a conductiveand chemically stable support (for linking between the metal andpolyaniline or PANi) for the electrochemically synthesized polymer.Although conductive polymers have been synthesized over hard, polishedcarbon substrates, it is here discovered that conductive polymers can beelectrochemically synthesized onto graphite micro-particles on basemetals while maintaining the electrical performance of a film grown ontonoble metal substrates. The graphite micro-particles create a linkbetween the base metal and the PANi film to afford a method forattaching PANi to surfaces that have up to this date proven extremelydifficult to achieve in non aqueous environments.

Graphite or graphene can be applied to the thin metal electrode by abuffer pad at high speed, either in a random, circular or unidirectionalpattern. For example, a moving belt or orbital buffing device (e.g.4000-11000 rpm at 1-20 psi) can be used. The thickness of the carbonlayer so produced in 1 to 10 seconds of application can be uniform,continuous and 10 to 100 nanometers in thickness.

An example of a suitable buffering process can be adapted from U.S. Pat.No. 6,511,701, which is incorporated herein by reference. In theprocess, dry carbon particles can be applied to a metal, preferablyaluminum, surface uniformly. In the present invention a buffing pad canbe moved in the plane of the substrate parallel to the substratesurface, or surfaces. The random orbital motion of the pad in thepresent invention is carried out with its rotational axis perpendicularto the substrate or web. Since the electrode is moving in thelongitudinal direction, a simple linear or back and forth motion in thelatitudinal direction will also suffice. The coating does not requirethe heating step described therein. Further, the units can be modularsuch that by stacking multiple units on top of each other, both sides ofthe substrate can be coated such that a first side is coated in a firstunit and the film is then directed (up or down) to a second unit wherethe opposing side is coated. A hardened stainless steel pressure plateis used to apply a uniform and controllable pressure to thefilm/vibrator pad interface. The modular units are sealed and kept undera negative pressure to keep the graphite powder contained.

The electrochemically grown polymerization begins immediately on thissurface, produced over metals, such as aluminum. The adhesion of thesynthesized polymer on this carbon imbedded surface on aluminum, asmeasured by a cellophane tape pull-off test, is good, and the electricalstability of the film is good through 6500 cycles in non-aqueouselectrolyte. It is preferred that the carbon micro particulate (lessthan a continuous film) be formed on as received oil-free aluminum.Cleaning the aluminum with e.g. phosphoric acid or sodium hydroxide willalter the native oxide and alter the performance of the film duringsynthesis initiation due to the heavy aluminum oxidation currentproduced. If the aluminum is fresh (without any oxide), then acontrolled partial oxidation can be achieved with steam, hot air, etc.,treatments known in the art. Preferably the native oxide is establishedprior to carbon imbedding, but it is possible to oxidize the aluminum ina second step following carbon imbedding. Preferably the aluminum may beensured to be oil-free via exposure to corona discharge.

In case of the use of a chemical linker, the growth of the conductivepolymer on non-noble metals can be described as five steps: 1) The metalsurface of the support is stripped bare to (or provided as) anon-oxidized metal; 2) Hydroxylation is achieved in order to facilitatea chemical reaction; 3) A bifunctional agent is linked onto the surface(A chemical having or involving two functional groups or binding sites);4) Polymer growth is initiated onto the linker or bifunctional layer;and 5) Polymer growth is proliferated. A lesser set of steps may bedesired for noble metal applications. A more detailed explanationfollows:

1) In order to clean the substrate down to bare metal, either mechanicalmeans (e.g. brushing or polishing) or chemical means such as 3:1 roomtemperature HCl:HNO₃ in water solution for a number of seconds (e.g. 15seconds) is performed. Other immersion times such as five seconds or 200seconds are also possible, but too little time does not clear the oxideand too much time may remove too much metal. A corona discharge may alsobe applied in order to remove hydrocarbon material.

2) In order to Hydroxylate Nickel, for example, the metal surface isimmersed in 1 molar KOH with several (e.g. 2 or more, such as between 3and 10) cyclic voltammetry cycles between 0.2 and 0.5 volts re. Ag/AgCl.The rate can be conveniently applied at 20 mV/sec in a basic solution,such as a 2M aqueous NaOH solution. There are other ways to HydroxylateNickel, for example with the use of bases at elevated temperature. TheCV method is preferred since it avoids conditions where excessiveoxidation takes place. Aluminum, Titanium and other metals can also behydroxylated by treatments with various bases such as Sodium Carbonate,metal Hydroxides, etc. The hydroxylated product can be rinsed, ifdesired.

3) In order to prepare a stable and favorable surface to polymer growth,a chelating or bifunctional agent-containing solution, such as Phthalicor Phosphonic acid can be used. Bifunctional agents include compoundswhich will react with the support and, directly or indirectly, with themonomer. Phthalic acid results in a covalently attached, organic,hydrophobic linker upon which the polyaniline can readily grow. Themetal Hydroxylated surface from step 2 is immersed in the linkersolution (that may include additives such as acetonitrile to guardagainst premature loss of protons) at an elevated temperature forseveral seconds or minutes (details to follow). This reaction can beperformed in a dry organic solvent, such as DMSO. Suitable temperaturesinclude 65° C. for about 10 min, for example. Other temperatures andreaction times can be used as well with acceptable results. In this way,the surface of the non-noble metal substrate is made ready forconductive polymer deposition. The films can be rinsed in an organicsolvent and, optionally, dried. The films can be used immediately orstored, for example, in a container with a desiccant. Subsequent tothis, the linker can be subject to delamination if the pH or pKA is toohigh and must be preserved.

Polyaniline can be grown on either the cgg layered electrode or thechemically modified electrode. Polyaniline grows in at least two phases(MacDiamid), lateral surface coverage, and vertical or connected growth.The chemical reactions that take place initially to cover the surface ofthe substrate (in the preferred case the linker layer) are thought to bedifferent than in full growth phase. The electrochemical potential thatdrives the early or templating phase reactions can also be different. Inorder to stimulate good adhesion and high surface area morphology, a CC(constant current) or CV (cyclic voltammetry) step may be used toestablish a seed or templating layer for the conductive polymer.

High speed growth is achieved with the benefit of a good template orseed layer formed above. The nature of a good template layer ischaracterized by good adhesion, electrical conductivity, and a surfacethat promotes high surface area morphology growth. PS (potentiostatic)or CC (constant current) growth conditions are selected since they arenearly twice as fast as other methods, and more preferablypotentiostatic mode is preferred since the growth is independent of thesubstrate surface area. Multiple potentiostatic growth regions, atprogressively higher voltages, may be preferred to further accelerategrowth. A further explanation of this rapid phase growth is given below.

The method provides for the deposition of a high surface area,conductive polymer, such as polyaniline, synthesized directly onto theribbon or substrate using a combination of electrochemical synthesistechniques selected from: Potentiostatic (PS), Constant Current (CC),Pulsed Potentiostatic (PP), Cyclic Voltammetry (CV). The following is adiscussion of the advantages and disadvantages of the various methods.

PS growth is very fast and proliferates an existing morphology but oftenaffords a delayed initiation of growth. Delayed initiation can lead toan oxidized surface on the metal substrate, poor adhesion, and lessdesirable morphology compared to nanowires. PS growth can direct energytoward the desired reaction if it is well identified. CV growthstimulates many different reactions on the surface and can help initiatefavorable reactions less well defined and missed by PS growth such as adesirable template for high surface area polymer growth. CV also isslower in overall growth rate when compared to PS or CC. CC growthallows for self selecting reactions; i.e. the reactions on the surfacedetermine to a large extent the resulting voltage. PP is slower than PSbut creates higher instantaneous currents. This can be useful if thevoltage and time span of the pulse is varied over a range that includesfavorable reactions. In a way, this is similar to the CV method. Theoverall conductive polymer growth disclosed utilizes one or more, suchas two or more of these methods to achieve high quality seed layers andsustained rapid growth necessary for production applications.

The conductive material is a polymer produced in situ. Conductivepolymers include polyisothianaphthene, polypyrrole, polythiophene andpolyaniline and substituted or unsubstituted derivatives thereof.However, polypyrrole, polythiophene and polyaniline containing polymersand their substituted and unsubstituted derivatives are preferred forthe present invention because they are inexpensive and easily handled.Polyanilines are most preferred. The focus herein is polyanilines.However, the polyanilines can be substituted with the other polymers.

The disclosed method can allow for complete growth within about 5-90minutes, depending on amount of growth desired and growth conditions, onan optionally moving segment of the substrate or metal ribbon.

The Physical Growth Procedures:

Electrochemical baths motivate ions to flow within the electrolytesolution and electrons to flow in the conducting electrodes andconnecting wires according to the voltage presented. The voltagepotentials created between the various electrodes are fairly local dueto the IR losses within the liquid and therefore separate electrodes canbe used to define different conditions of voltage in order to controlthe flow of electrons and ions to and from the electrode surfaces. Thesupport or ribbon-like working electrode is passed through or subjectedto a first reaction zone or bath where PS, CC, PP, or CV is applied. Thesupport is then optionally passed through or subjected to a secondreaction zone or bath where PS or CC is applied. Subsequent additionalreaction zones may follow. The support or working electrode ismaintained in a grounded state with relation to the auxiliaryelectrodes. More than one counter or auxiliary electrodes are eitherexposed to the fluid bath directly or separated by a membrane or glassfrit. Each one of the auxiliary electrodes comprises a zone in thepreparation bath. CC, CV and PP have proved useful in initiating ornucleating growth and promoting a highly desirable nano-texturedmorphology having a very high surface area. By using at least one cycleof the CV method, a few seconds of the CC method, or at least one pulseof PP method, an improved conductive polymer electrode growth initiationcan be made with high efficiency. Since the moving ribbon electrode isheld at or near ground potential and the voltage potential created bythe proximity of the counter electrodes in the synthesis bath is fairlylocal due to the IR characteristics of the electrolyte, areas of asingle bath can be held at different potentials, creating differentgrowth results.

FIG. 3 is shown as an example of growth zones created by multipleelectrode arrangements. There may be several zones created to refine theapproach. The first zone of the bath (see FIG. 3) has at least oneworking electrode, at least one counter electrode and at least onereference electrode. The working and/or counter electrode are configuredsuch that one can alter the voltage potential between them. In the firstzone (initiation), PS or CC or CV or PP can be selected. In the secondzone (growth), PS or CC can be selected.

For example, when polyaniline is being produced, the voltage potentialcan be changed between about −0.2 and 1.2 volts versus a referenceelectrode such as Ag/AgCl (SCE or SHE can also be used). As the ribbonpasses through this zone, it is exposed to a voltage potential that ischanging, for example at a rate of at least about 5 mV/sec, preferablyat least about 100 mV/sec, such as about 300 mv/sec over the rangestated. Other combinations are also possible. The surface of the ribbonsubstrate begins to grow polyaniline essentially immediately at variousoxidation states, while avoiding substantial oxidation of the supportmetal. Thus, the invention comprises contacting the support comprising aconductive metal (which preferably has been previously treated eitherwith a cleaning, Hydroxylation and/or bifunctional agents, orbuffed/rubbed with carbon such as graphite or graphene) with a solutioncomprising a monomer characterized by multiple oxidations states andcapable of producing a conductive polymer in the presence of at leasttwo electrodes wherein the voltage potential or current is alteredbetween one or more, such as two or more, voltage states. The CV, CC orPP methods are best used in this initiation phase. As opposed topotentiostatic growth at 0.825 volts vs. Ag/AgCl, where the polyanilineis grown in its near fully oxidized state, the CV method for examplegrows polyaniline in a full range of oxidation and reduction stateswhich aids in the even initiation of growth on various substrates, evenon non-noble metal supports, where usually oxidation inhibits polymergrowth and adhesion, and particularly on the prepared surfaces asmentioned earlier. A desired nano-textured morphology can be formed moreconsistently and more quickly using CV, CC and PP. The reaction isgenerally completed very quickly and complete seeding of the support canbe completed in about 1 to 100 seconds, such as 1 to 60 seconds.

In one embodiment, the film can be submerged into a low pH aqueoussolution containing aniline and, for example, camphor sulfonic acid, andsubjected to a 60 second constant current pulse, for example at 1mA/cm², that initiates growth of polyaniline “buds” onto the linker end.The resulting Ni/4-APA/PANi film can then be dried, preferably, underlow oxygen conditions and transferred to an organic electrolytesolution.

The seeded support can then be subjected to a second reaction zone orbath where the polymer continues to grow in the presence of an appliedvoltage PS or CC. The method can then be used to proliferate the desiredmorphology quickly (about twice as fast as the CV method) which isimportant to reducing manufacturing cost. In this step, the voltageand/or current is maintained to optimize polymer growth. In the exampleof aniline, the voltage potential is maintained such that the aniline isfully oxidized, preferably at about 0.8 (e.g., 0.825) volts, vs.Ag/AgCl. The step can be potentiostatic (PS) or galvanostatic (CC).

In another embodiment, the cgg-film can be submerged in anelectrochemical cell with an electrode, e.g., a Ni counter electrode,arranged so that it envelopes both sides of the working electrode. Astandard Ag/AgCl electrode can be used as the reference electrode.Camphor-10-sulfonic acid β or other sulfonating compound, can be addedto the growth solution and the pH can be adjusted. A low pH ispreferred, such as 1.3, and can be readily accomplished by addingsulfuric acid. The Al/C working electrode is placed in the growthsolution between two Ni counter electrode plates with the distancebetween counter electrode and working electrode approximately 1 cm.Constant potential method can be used to grow polyaniline films on Al/Celectrodes at 0.75 V vs Ag/AgCl reference. It is noteworthy that thisgrowth voltage can be 50 mV lower than with growth on platinum or otherbare metal electrodes. The film can then be rinsed with or withoutvacuum and/or dried.

The polymer growth step can be maintained until the desired degree ofpolymer growth has been achieved. Typically, the reaction will bemaintained for at least about 1 minute, preferably at least about 2, 3,4, or 5 or more minutes, up to an hour or more.

The first and second growth reaction zones can be in the same vessel ordifferent vessels. Preferably, the zones are in the same vessel and/orin fluid communication. It is particularly advantageous that the zonesare in the same bath using a single solution.

The solution in the bath contains monomer and a solvent. The solvent ispreferably aqueous. The monomers are preferably a substituted orunsubstituted aniline or pyrrole, preferably unsubstituted aniline. Themonomer is preferably added and/or maintained in solution, preferablyapproaching or at saturation. For example, aniline can be added and/ormaintained in an amount of about 0.4M.

The solution optionally contains an additional acid, such as a strongacid including but not limited to HCl, HF, nitric acid, oxalic acid,sulfuric acid or a sulfonic acid. Sulfonate donors, such as sulfonicacids, including camphosulfonic acid and toluene sulfonic acids andcombinations thereof are preferred. The acids are preferably added in amolar ratio of acid to monomer between about 0.5:1 to 3:1. Preferably,the acid is added in an equimolar amount to monomer.

The solution can additionally optionally contain an oxide dopant such asan oxide of Manganese, Vanadium, Iron or Cobalt. Such additionalmaterials can be incorporated onto the surface of the electrode in orderto improve the capacitance and voltage range performance of thepolyaniline or other polymer. Oxides of Manganese, Vanadium, Iron,Cobalt, etc. are commercially available from Aldrich, Waco and the likeand can be placed in suspension during the synthesis process. Since theelectrolytic performance of the oxides will partially superimpose theperformance of the polyaniline, they can work together. The electricalconducting capability of the polyaniline comes along with its redoxcapability, and therefore there is no dead weight as in the Carbonand/or plasticizer used in Lithium ion batteries or othersupercapacitors. This feature can improve the specific energycalculation. It is also possible to co-synthesize oxides of e.g.Manganese and Vanadium from their Sulphates along with the precursors ofpolyaniline or polypyrrole etc. Expanded voltage range can be thusachieved by superimposing the redox characteristics of both types ofmaterials. Typically, the polymer establishes the morphology, and theoxide forms on the surfaces of the polymer.

The reaction can be readily completed at room temperature, e.g., about20° C., although other temperatures can be selected as well to optimizeyields, reaction times or control polymer growth. The pH of the solutionshould be controlled for consistency. The pH can be optimized for thespecific reaction and is generally less than 6.0. In one example, a pHof about 1.8 can be used. In general, a pH between 1.2 and 1.8 can beused.

The product produced by the method can then be used directly to make thefinished product or can be subjected to further processing. Preservationof the Oxidation state of the film is advantageous. For example, themethod can further comprise a washing and/or drying step. Washing can beaccomplished by passing the support through a low pH water solution,electrolyte solution or volatile organic solvent to preserve the levelof film protonation. A preferred method of preparing the film foroperation in a non-aqueous electrolyte is to use a hydrazine rinse. Thisrinse occurs at room temperature and causes a stripping of all growthrelated anions while providing for a fully hydrogenated, reduced film.This strategy allows for a most efficient transformation of theconducting polymer to switchable forms in the non-aqueous electrolytesolution. It also is purely chemical and does not require electrodeapplication. By cycling the conductive polymer in a new, say lithiumsalt/PC solution, a new anion system can be established inside thepolymer system. Drying can also be achieved by controlled application ofconvective or radiant heat between about 20 and 200° C. and throughexposure to very low dew point dry air, or exposure to a vacuum.

The process can be preferably conducted continuously orsemi-continuously. In such an embodiment, the reactants can bereplenished into the solution continuously or semi-continuously. Wherethe first and second reaction zones are in liquid communication or inthe same bath, the solution may be homogeneous.

In another embodiment, polyaniline nanowire electrodes are synthesizedon base metals, and show stability in non-aqueous systems. Suchpolyaniline nanowire electrodes, when tested in non-aqueous electrolytesystems, demonstrate 1000 F/g of active material (F=Farad).

Typical Growth Solution and Conditions:

0.1 M Camphosulfonic acid; 0.1 M p-Toluenesulfonic acid; 0.45M Anilinein DI water. Growth is achieved at 25 degrees C., with CV between −0.2and 1.2 Volt vs. Ag/AgCl reference at 300 mv/sec for one cycle. Then PSfor about 2400 seconds at 0.75 Volt vs. Ag/AgCl reference is performed.The working electrode can be Titanium, Aluminum, Nickel, Stainlesssteel, Silver, Platinum or Gold, graphite covered aluminum beingpreferred. The counter electrode can be Nickel, Stainless Steel,Platinum or Gold, stainless steel being preferred. The referenceelectrode can be SHE, Ag/AgCl, SCE, etc, Ag/AgCl being preferred.

The methods described herein can result in nanoporous growths havingsuperior properties and characteristics. Conductive polymeric nanowirescan be readily grown in equal parts Aniline and strong acids. It isfound that greater stability is afforded in the disclosed mixture: Thepreferred synthesis solution has one part Aniline to the sum of the CSAand p-TSA to optimize the morphology, redox activity and stability ofthe film. The selected concentrations are 0.45M monomer/0.1 M pTSA/0.1MCSA in a water solution. Another preferred solution contains only CSA at0.2 M and aniline at 0.45M (0.45 M aniline is essentially a saturatedsolution). In one example, nitric acid or another strong acid can beused to adjust the pH of the solution to about 1.3. The CV/PScombination also provides greater adhesion which is important tosubsequent processing.

Product Characteristics:

The products formed by the process can be characterized as having a veryhigh surface area and are highly porous, as evidenced by visualinspection, as below. The polymers are nanowires or nanofibers in thatthe diameters of a substantial number (e.g., at least about 50% and morepreferably at least about 70%, such as at least about 90%) of strandsformed thereby are less than 1 micron, preferably less than 500 nm andmore preferably less than 200 nm. The pores and interstitial spacesformed by the nanowires are relatively large, in comparison to thefibers, the diameters of which are often 4 times or more the diameter ofan adjacent fiber.

The polymers are conductive to the surface of the electrode and possessgood to excellent adhesion properties. The surface area of the structurecan be measured using nitrogen absorption, as is known in the art andcan be preferably at least about 200 m²/g, such as at least about 500m²/g, or more preferably at least about 1000 m²/g. Maximizing surfacearea improves ion capture when the polymer is in contact with anelectrolyte solution. For example, the polyaniline electrode made inaccordance with the method above can produce about 4 volts in an organicsolvent containing 1 M lithium salts when mounted opposite a suitableLithium or Lithiated metal electrode such as Aluminum or Tin. In anaqueous electrolyte solution, a 2 volt cell can be produced with thepolyaniline electrode on each side of the cell.

FIG. 4 illustrates the nanowire and highly porous nature of the product.

Good adhesion is defined as a film that continues to operate withoutdegradation over thousands of use cycles (see operating curve belowshowing up to 25,000 cycles of polyaniline operation withoutdegradation).

Lithium ion batteries, with positive electrodes of Lithium insertedCobalt, Iron Phosphate, MnO₂ etc. for comparison can operate forhundreds to low thousands of cycles with up to 30 percent degradation.The TEM above is typical of the delicate nano-structure of stabilizedPolyaniline.

The products of the invention have good to excellent resistance to cycledegradation. The products are resistant to cyclic voltammetry testing.Resistance can be measured by immersing the polyaniline sample in a halfmolar solution of Lithium salt, such as LiBF₄ in 50% PC/AN electrolyte,and cycling between its operating voltage of −0.2 and 0.9V re. Ag/AgClat 1000 mv/sec scan rate for 5, 10, and 20K cycles. The products of theinvention are characterized by less than 10%, preferably less than 5%,degradation or current loss over 2,000 (preferably over 5,000 or 10,000)cycles applying a voltage potential of 50 mV/sec, such as 100 mV/sec, or1,000 mV/sec. The percentage degradation can be calculated bydetermining the difference in the areas under the curve before and afterthe stress tests are conducted.

The improved properties of the products described herein are due in partto the homogeneous deposition of acid groups, e.g. sulfonate groups,along the polymer structure. Thus, the invention provides for electrodescomprising a support comprising a conductive material and a conductivepolymer, characterized by a sulfonate concentration within 1 micron(preferably within 0.5 microns) of the support surface that isessentially the same as the sulfonate concentration within 1 micron(preferably within 0.5 microns) of the electrode surface. “Essentiallythe same” concentration is intended to mean herein that the sulfonate tomonomer ratio at the two loci is within about 50%. Thus, if thesulfonate to monomer molar ratio at the surface is about 0.5:1, then thesulfonate to monomer molar ratio at the support is between 0.25:1 to1:1.5. In another preferred embodiment, the sulfonate to monomer ratioat the surface and at the support (within 1 micron, preferably within0.5 microns) are both approximately 1:1.

In order to preserve the level of dopant anions in the film electrodeduring transfer out of the aqueous growth solution and into the organicelectrolyte, the film is left in the fully charged state. This ischaracterized by a dark green color, and represents full oxidation.Although the large anions leave the electrostatic attraction of thepolymer during discharge, they are physically trapped unless they areinadvertently washed away during the transfer process. It was found thata fully charged film would provide greatly enhanced cycling enduranceonce transferred into organic electrolyte. Another and most preferredstrategy is to strip the anions from the film while preserving the levelof hydrogenation by using a 5% Hydrazine rinse. In this condition, theconductive polymer is stable chemically in the reduced state and iswhite or cream in color. A high percentage of the repeat units are nowavailable to be made electrically active in the new anion systemprovided by non-aqueous electrolyte solution.

Manufacturing Improvements:

During the polyaniline growth in the aqueous growth bath, the nanowirestructure is fragile and subject to damage. In order to minimize therisk of damage to the growing film, care should be taken in the handlingof the film as it travels through the growth bath. Potential damage tothe film can come from contact with the guiding/turning rollers, contactwith the electrode plates, induced surface shear from fluid flow andnormal (pressure) forces on the film. The mechanical design of thegrowth tank preferably accounts for all these possible modes of filmdamage over the entire operating range. During normal operation, thefilm can be traveling at a speed of 10-20 cm/sec, and the design canalso handle zero speed conditions and start up/speed up and stop/slowdown transitions without damage to the films. To accommodate thesedesign requirements, a number of design approaches are preferred.

First, guide rollers or turning bars can be used to change the directionof the film in the growth bath. For a single layer growth, eitherhorizontal or vertical, the guide rollers are used to direct the filmfrom the external source, down into the growth medium, through theelectrode plate path, and then back out to the film exit. A basicvertical arrangement uses at least one guide roller in the growthmedium, and a basic horizontal arrangement uses at least two guiderollers in the growth medium. In both cases, vertical and horizontal,the external routing of the film into and out of the tank will alsotypically use guide rollers.

Typical film tensions will be in the range of 2-10 N (0.4 to 2.2 lbs)and this tension can be maintained at all times during the manufacturingprocess, and all film speeds from stationary to maximum velocity. Thefilm tension can be maintained by components external to the growth tanksuch as core shafts, pneumatic shaft brakes and clutches, tensionsensing rollers and closed loop tension controllers. Nimcor and Montalvosupply such equipment. During normal processing speeds, the film can bepulled into the tank, around the guide rollers, through the electrodefield plates and back out of the tank. While the tank design illustratedherein has been for horizontal processing of the film between horizontalfield plates, vertical designs can be used as well.

While the film is pulled around the guide rollers (FIG. 19), there isrisk of damage to the film surface through a skidding contact(differential motion) of the film against the roller surface. There areseveral ways to minimize the risk of this type of damage. Even thoughthe substrate and growth structures are very thin, when the film ispulled around the roller, the neutral axis for bending will exist closeto the center of the film and the inner surface (surface facing theroller) will compress and the outer surface will be placed in tension.This compression as the film is pulled from a straight condition into acurved state will cause some relative motion of the film surface againstthe roller surface. This motion can be minimized by making the rollerdiameter very large compared to the film thickness. The guide rollersare typically in the 75-100 mm diameter range to help minimize thisrelative motion of the film surface compared to the roller surface andneutral film axis. A more important source of differential motion iscaused by differences in motion between the film and the surface speedof the roller. The rotation of the roller can be driven by the motion ofthe film through shear stress, or the roller can be driven by anexternal source such as a motor. In the case where the roller is drivenby an external motor, a control and drive system can be built to matchthe roller velocity to the film velocity, but small variations due tocontrol errors will always be present, especially during periods ofvelocity change were the film is either speeding up or slowing down.Even if the roller and film are driven by the same motor drive,rotational inertia and drive backlash conditions can cause momentaryvelocity differentials. In the case where the film drives the rollerspeed, there can be an induced shear force on the film surface totransfer the required torque to overcome the bearing and fluid drag onthe roller. During a velocity change, the shear force between the filmand the roller will also have to account for overcoming the rotationalinertia of the roller. Very slow acceleration and deceleration can beused minimize this induced inertial drag on the film surface, but thisleads to long transition times which can make controlling the growthprocess between the field plates very difficult.

A better solution to minimizing the surface shear on the film and toeliminate the risk of a differential skidding motion is to create afluid layer between the film and the roller surface. FIG. 19. This fluidlayer can support the film, preventing contact to the roller surface anddue to the low viscosity of the aqueous growth solution, velocitydifferentials between the film and roller will create only very smallshear forces on the film surface. At running speeds, it may be possibleto use entrained fluid on the roller to produce this fluid layer, butfor protection over the entire operating film speed range, the fluidfilm is maintained using an external mechanism. By pumping fluid throughthe roller surface from the roller inner diameter to the outside, afluid film can be maintained, even at zero film speed. Also, by doingthis, the rate of pumping can be controlled to accommodate varying filmtensions.

For a given line tension T, the preferred pressure to produce a fluidgap can be estimated using the following equation:

2·T=∫ _(o) ^(π) P(θ)·w·r·sin(θ)dθ

where P is the local gap pressure, w is the film depth into the page andr is the roller radius. For a simple initial calculation, one can assumethat the pressure is constant around the circumference and the equationbecomes:

2 ⋅ T = 2 ⋅ P ⋅ w ⋅ r or $ P \sim\frac{T}{w \cdot {r.}}$

Thus, for a 10 N tension with a 20 cm wide film on a 75 mm diameterroller, the preferred pressure would approximately be 667 Pa (0.1 psi).These low pressures are very easy to establish and minimize thedifferential pressure across the film as well.

A system has been designed that incorporates a perforated roller onto adriven hollow shaft. Fluid is pumped into the hollow shaft throughrotary unions. This fluid then enters the inner diameter of the rollerand exists through the holes in the roller shaft. An isometric view ofthis roller is shown in FIG. 20. In a preferred embodiment, the fluid isa reaction medium.

The guide rollers described herein can be used in other methods fortransporting fragile or thin sheets of material through liquid or fluidsolutions.

The electrochemical growth tank can employ one or more potentialelectrodes. Preferably, the process employs plates with multiplepotentials for initiating, growing and conditioning the polyanilinestructure. Use of multi-potential electrodes will facilitate acontinuous roll fed foil system. (FIG. 21). Further, the electrodes canbe configured serially and/or stacked. Preferably, the process employsrows of horizontal electrodes stacked in vertical series. The low shearroller structures allow the foil or film to be wrapped back and forthwithin a single tank and reduce the total line length significantly.Each electrode in a horizontal set can be at the same or differentpotential and each vertical series can also have the same or multiplepotentials.

In a batch process, there is a single electrode to which differentpotentials or current conditions can be applied in order to obtain thedesired result. In this case, the operating conditions can change withtime and can include constant voltage, constant current and constantpower operation. With a continuous foil process, time varying conditionson a single electrode or set of electrodes is not optimal. Instead, thesystem preferably uses a series of electrodes at different conditionsthat the foil is pulled past. By changing the conditions from one plateto the next, an effective time varying condition can be applied to anyfixed point on the film.

FIG. 21 shows a system with layers of electrodes, in which there arethree separate sets of electrode plates per layer. Each set of platesconsists of an upper and lower plate such that both sides of the film isexposed to the same potential. The electrodes are preferablyelectrically isolated from each other. They can all be connectedtogether externally in order to be run at the same operating condition,or each set can be run at an independent operating condition. FIG. 21illustrates a device where a film can be fed past the input roller,around the guide roller between a first set of electrodes, between asecond and third set of electrodes configured in a horizontal series,exit the electrode set under and around a second guide roller and backthrough a set of three serially configured sets of electrodes. Thesesets of electrodes are configured vertically above the first series ofthree sets of electrodes. The film can then exit the assembly to underand around a third guide roller and back into a third series of threesets of electrodes and so on. Five layers of three sets of electrodes isshown. FIG. 21 also illustrates the tank and frame for the electrodes.

The length of each electrode set can be consistent between sets or canvary from set to set. For a given foil speed, a series of shortelectrodes sets spaced closed together can be used to produce a rapidlytime varying voltage or current condition. Long electrode sets ormultiple sets that are electrically connected can be used to producetime constant voltage or current conditions. The size of the gap betweenthe electrodes in a set can be varied depending on the film speed, sizeand length of a single layer. For a given film tension, the film cannotbe allow to contact the electrodes, so as the length of the single layerincreases or as the density of the tank fluid decreases or as thethickness of the film increases, the size of the electrode gappreferably increases to accommodate increased dropping of the film. Ingeneral, a 10 mm gap will handle all possible film/fluid/tensionoperating conditions. Making the gap too large will negatively impactthe size of the overall system as well as increase potential electrodeedge issues in terms of a degraded electric field in the growth fluid.

The gap between successive sets of electrodes is dependent on the fluidproperties (resistance/length) and the electrode potentials. As theconductivity of the fluid increases, or as the electrostatic potentialbetween successive sets increases, the minimum allowed gap between thesets preferably increases to prevent excessive leakage effects from oneset of electrodes to another. Even for conditions where there is asingle potential to be applied to the electrodes, the system ispreferably split up to a series of independent electrode sets that areindependently controlled. As concentrations of chemicals and salts vary,the effective potential of an electrode set compared to the local filmcan vary. In order to keep the local electrode set at the correctpotential, a reference electrode may be used to account for varyingfluid conditions. Especially in cases of very long layers at a singlepotential, the local reference can be used to keep a tight tolerance onthe effective electrical potential and the system can be broken downinto a series of independent electrode sets that will run at similar,but not exactly the same, potentials.

Another factor that may benefit from the separation of the electrodesinto multiple sets is the grounding requirements of the conductive film.As the film travels through the tank and is either plated, or has apolyaniline structure grown on it, an electrical current is passed intoor out of the foil, depending on the operating conditions. Thisaccumulated current must complete the driving circuit and be conductedto the opposite power supply terminal from the electrode set. Thisrequires a regular mechanical/electrical connection from the film to thepower supply terminal. As the current flows through the foil to thiscommon collector point, the current flow will induce a voltage potentialin the film. If the distance along the film between successive collectorpoints is too high, then the induced voltage drop can be high enough tostart to affect the plating or growth process. For example, if you havea 10 micron thick aluminum foil (1145 alloy, for example), that is beingsubject to a constant current state of 1 mA/cm² per side with a totallength between grounding points of 1 m, then the maximum potentialdifference along the film will be approximately 7 mV. If the current orthe length is doubled, then the maximum potential difference along thefilm will be 14 mV. If the process requires a voltage potentialvariation limit of 10 mV, then the first instance may be tolerated, butthe second would require breaking the electrodes into multiple sets withfilm grounding in between the sets.

Another benefit to breaking the electrodes into sets is to allow formulti layer tank structures. For a required residence time of a foil ina plating or growth potential, the required wetted length of theelectrodes is a given. For example, a required residence time of 2minutes for a film traveling 10 cm/sec will require a total wettedelectrode length of 12 m. For a single layer approach, this wouldrequire a tank of 12+ meters in length. By breaking the electrodes intosets and then stacking multiple layers of sets in a single tank, theoverall tank length can be reduced significantly. If the previousexample is broken into 4 layers, then the total layer length would be 3meters and the tank might be 3.5-4 meters total. Due to the verydelicate condition of the polyaniline in the aqueous state during thegrowth process, this can be facilitated by using the low shear guiderollers/turning bars described above.

Two electrodes composed of polymer synthesized as described above can bemounted opposite each other, separated by electrolyte and asemi-permeable membrane in order to make an electrolyticsuper-capacitor. For example, the ribbon electrode can be cut intoshapes facilitating assembly. One example is the use of laser cuttingthat includes the forming of an outer shape and the electrode contactinghole or spacer. Material including the punched sprocket holes can beretained or discarded after trimming. A vacuum handling device can beused limiting contact to small portions of the electrode sheet.

An example of an assembly is enclosed where sheets of electrodes areseparated by semi-permeable membranes. The sheets are wetted with anelectrolyte mixture, for example, by air-free atomization or submersingthe electrodes into an electrolyte solution. Air-free atomization canavoid the use of vacuum filling techniques that can harm thenanostructures. The electrolyte easily wets through the semi-permeablemembrane and into the polymer electrode, controlling excess fluid.

In the case of a product with opposing polyaniline electrodes, aqueouselectrolytes can be used. Such products can operate between 0 and 2volts, for example. The electrolyte solution can be an ionic liquid,e.g., a room temperature ionic liquid such as1-butyl-3-methylimidazolium chloride, sulfuric acid, potassiumhydroxide, sodium hydroxide, propylene carbonate, dimethoxy ethanol,diethyl carbonate or acetonitrile. As further examples, the liquid mayinclude LiClO₄, NaClO₄, LiAsF₆, LiBF₄ or quaternary phosphonium salts.

In the case of higher voltage operation (e.g., 4 volts) usingpolyaniline and Li/Al requiring high breakdown field operation,electrolyte solutions such as propylene or ethylenecarbonate/dimethoxyethane (PC/DME, such as 50/50 PC/DME) and Lithiumsalts such as LiBF₄ can be used. Additionally, a large negativeelectropotential material can be selected as the opposing electrode. Asis typical for a Lithium ion battery, a Lithium based negative electrodecan be used. Lithium ions can be inserted into Carbon or Graphite whichresults in an electrode of about −3 Volt. Lithium ion batteries sufferfrom overheating and sometimes explosion due to the use of over −3 voltsconditions during charging. Since −3 Volts represents a decompositionVoltage for Propylene Carbonate as well as other organic electrolytes,it is desirable to find a safer negative electrode if possible.

The inventors discovered that safer negative electrodes can be made byinserting lithium into an aluminum electrode. In this embodiment,aluminum, and alloys thereof, can be selected as a Lithium ion insertionmaterial since its alloyed electro potential is about −2.7 Volts, wellwithin the “safe organic electrolyte operating window.” The aluminum ispreferably a magnesium containing alloy. The alloy is lithiated byflowing a reducing current (e.g. 5 ma/cm²) in a preferably moisture freeorganic electrolyte containing a Lithium salt such as LiSO4, LiBF₄ orLiClO₄. The lithium salt is preferably maintained in a solution of atleast about 0.5M, preferably about 1 Molar solution. An organicsolution, such as PC/DME as above can be used. The dried Aluminum can belithiated as described above or by physical application with an airinsensitive Lithium compound such as SLMP (Stabilized Lithium MetalPowder) from FMC Corp. In the latter case, the Lithium is alloyed intothe Aluminum by rolling or contacting with electrolyte solvents. Asspecified by Melendres in U.S. Pat. No. 4,130,500, which is incorporatedherein by reference, Magnesium can help physically stabilize Aluminumfilm during the swelling and shrinking phases of Lithium insertion andremoval, respectively.

Specifically, an alloy composition of about 1, preferably 2 atom percentmagnesium to 20 atom percent magnesium and aluminum can be used. Atleast 3 atom percent magnesium can assist in maintaining structuralintegrity during electrical discharge when the lithium atoms migrate tothe electrolyte. Examples of specific Aluminum alloys include 5083 and5052. Since the magnesium does not enter into the cell reaction, itappears to serve in interstitial or substitutional solid solution as abonding material for maintaining a matrix structure into which thelithium can be repeatedly charged. Magnesium concentrations arepreferably less than 20 atom percent. Specifically, an alloy compositionof about 2 atom percent magnesium to 20 atom percent magnesium andaluminum can be used. At least 3 atom percent magnesium can assist inmaintaining structural integrity during electrical discharge when thelithium atoms migrate to the electrolyte. Examples of specific Aluminumalloys include 5083 and 5052. Since the magnesium does not enter intothe cell reaction, it appears to serve in interstitial or substitutionalsolid solution as a bonding material for maintaining a matrix structureinto which the lithium can be repeatedly charged. Magnesiumconcentrations are preferably less than 20 atom percent. As noted in theliterature (e.g. Schleich et al., J. Power Sources, 2001) the thinnestaluminum samples were less damaged in electrochemical tests. Themicro-porosity created as a result of the etch (described elsewhere)yields a similar result by improving the ionic access to the film whichin turn improves the cycling capability of the Li/Al alloy. In theetched aluminum film, the thinner walls (compared to a monolithicaluminum sheet) allows the aluminum to expand and contract with lessdamage. The source of the improved performance is thought to be areduced concentration gradient within the electrode.

Lithium is added to the aluminum-magnesium alloy in concentrations ofabout 5 to 50 atom percent. Lithium is preferably added to themagnesium-aluminum alloy electrochemically. This can be performed as theinitial charge within an assembled cell having sufficient reactionproduct, e.g. a lithium sat or chalcogenide, to provide lithium into thenegative electrode composition. Lithium and aluminum can also be mixedin a powder form and rolled into a foil, and annealed at 500 degrees C.for use.

Platinum can be used as the counter electrode (Ag/AgBF4 in PC/DME is canbe used as the reference electrode in the organic electrolyte). Anexcess of Lithium is inserted to the Aluminum to achieve a −2.7 voltelectrode (usually between 2-50% Molar content). The amount can beoptimized for the desired final current.

Although Lithium alloyed or amalgamated Aluminum is less sensitive tomoisture that Lithium metal, low moisture conditions such as −40° C. dewpoint air or Nitrogen gas are preferably used after the Lithiationprocess. In order to increase the surface interaction sites, theAluminum can be electrochemically roughened or etched in 1 M HCl, 5%ethylene glycol at room temperature with an oxidizing current of at 0.02A/cm² to form a very high specific surface area electrode whichincreases its current capability. Alternatively, the etch is between 10and 30 seconds at 80° C. Three minutes at room temperature is mostpreferred in order to provide the necessary surface area withoutweakening the substrate. The substrate is now dried at elevatedtemperatures of 80 to 120 degrees C. in dry air. In this way, a hybridsuper-capacitor can be made with up to a 4 Volt or so operation (e.g.−2.7 volt Li/AL plus 0.9 volt Polyaniline=3.6 volt operation) asillustrated below (FIG. 5) for a representative electrode system.

In another embodiment, a high surface area lithium-aluminum electrode isprepared by electrochemically etching an aluminum alloy employing anHCl-ethylene glycol solution. Examples of aluminum alloys include, butare not limited to, the 5xxx series, containing 0.3-5.0% magnesium.

The ribbon electrodes are advanced continuously through thepre-treatment, growth, etch or Lithiation baths before going through thedrying tunnel. The drying tunnel simply applies a ramped heating in airat between 20° C. to 200° C. gradually, to eliminate water from thematerial. Alternately, drying can take place by immersion in organicsolvents, and then dried as above. The simple, rinse free drying leavesbehind a certain beneficial level of acid salts as a further source ofdopant to the film.

Improvements have also been made to the drying step of the process.Drying the incoming material (+ substrate, − substrate and film layer)is important to minimize the introduction of moisture into the finalassembly area and into the final package. Since both the polyanilinestructure and the negative substrate are treated in aqueous solutions,there is a significant amount of moisture that has to be driven offwithout damaging the films. In order to do this, the materials can bepassed through an infrared (IR) heating oven with a preferablycounterflowing dry air/gas stream. Cross flowing streams can also beused. Use of long IR (2-10 micron) heaters helps to prevent damage tothe grown polyaniline structure which is sensitive to degradation fromvisible light. Also for drying the etched aluminum substrate, the use oflong wavelength IR will focus the energy on the resident water ratherthan the aluminum surface, which is highly reflective of long IR. Thecounterflowing dry air/gas helps to prevent the evaporated water vaporfrom entering the final assembly area and increases the drying ratecompared to IR heating in ambient conditions. Reducing the gap sizearound the foil helps minimize the required volume of dry air/gas andresults in a higher counterflow velocity for a given flow rate of air.

In one embodiment, a pair of IR lamps are mounted with their emittingsurfaces facing each other across a small gap (10-20 mm). The lamps aremounted into a frame assembly that has aluminum panels mounted on theoutside to create a sealed volume with either one or two entry gaps forincoming/exiting foil material. If a single gap on one side of thetunnel is used, then discrete sections of material can be inserted,dried and then removed. If a gap on both sides is used, then film can bepassed continuously through the tunnel. Each IR heater has an embeddedthermocouple sensor and its own PID temperature controller. Theoperating temperature of each heater can be independently set. There isa port on the side of the tunnel to allow for dry air/gas entry.

This small tunnel is sufficient for lab tests and basic development, butdoes not provide true counterflowing dry air/gas conditions. For theproduction line, the drying tunnel is the interface between ambientoperating conditions and a dry air environment. The dry air environmentcan be kept at a higher pressure than ambient to prevent humid air andmoisture from leaking into the dry air manufacturing volume. A narrowgap IR drying tunnel can have multiple heaters on the top and bottom(e.g., 2, 3 or more on each top and bottom) in an arrangement that canbe optionally hinged open for loading the film into the tunnel and foraccess to clean the IR heater surfaces for maintenance. By puttingmultiple heaters along the length of the tunnel, the heaters can be setat different temperatures if a controlled ramping of the filmtemperature is needed. In the case of a wet polyaniline film, rapidheating of the water and the substrate may lead to damage of the film,including up to the ablation of the polyaniline from the substratesurface. Multiple heaters allow for the controlled ramping of the energyinput into the films to help prevent this. Between successive heaters, ahighly reflective surface is used to reflect/reradiate any incidentenergy. These surfaces can typically be polished aluminum or stainlesssteel sheets, e.g., 1-2 mm thick. The position of the IR heaters withina module is flexible and can be arranged to optimize the drying of thedifferent films. If an unplated etched aluminum film needs to be dried,the heaters can be moved as far away from the film entrance as possible.This exposes the film surface to a period of dry counterflowing airbefore exposure to IR energy. This initial area of dry air will driveoff some of the resident water. Since the oxidation rate of exposedaluminum is highly affected by the presence of steam vapor, it may beadvantageous to drive off as much water from the film as possible beforestarting to drive up the surface temperature of the aluminum. For dryingthe polyaniline film, a gentle ramp up to temperature may be needed andmultiple close spaced IR heaters with each successive heater having aslightly higher operating temperature may be optimal. Gap sizing isimportant to keep to a minimum to reduce the volume of counterflowingdry air and to raise the air velocity relative to the film. As the airvelocity increases, the coefficient of convective heat transfer and masstransfer will increase, helping the drying process. Also as the dry airflows along the drying tunnel, it will pick up thermal energy from theemitters, reflectors and side walls. This increase in air temperaturewill help to increase the drying rate. FIG. 22 illustrates such atunnel.

Both dry air and inert gases can be used for the drying process. In somecases where the film may be especially subject to oxidation ordegradation from exposure to air, an inert gas such as N₂ or Argon maybe used to maintain a stable gas layer around the film. Minimizing thegap size will help to reduce the required gas volume.

The modular drying tunnel may also be stacked in series to develop amore flexible drying station for various conditions. The modular dryingsystem consists of series of drying tunnels in series with a guideroller assembly at the front and rear of the system. The tunnels can bestacked in direct contact to maintain an effective gas tunnel for thecounterflowing dry air. The guide rollers are used to ensure that thefilm remains in the middle of the air gap in the tunnel. If required,especially on long tunnels, guide roller assemblies can be place in themiddle of the drying tunnel system. The final set of guide rollers atthe exit of the tunnel are enclosed within a dry air enclosure that willmate to the final manufacturing dry air volume. This volume will be keptat a higher than ambient pressure and this pressure will induce thecounterflowing air stream through the drying tunnel. If a set ofintermediate guide rollers is used, it also has to be placed within adry air enclosure.

After drying, the ribbon electrode is cut into shapes facilitatingassembly. Examples include the use of laser and mechanical cutting thatincludes the forming of the outer shape and the electrode contactinghole or spacer. Material including the punched sprocket holes can bediscarded after trimming. A vacuum handling device touches only smallportions of the electrode sheet. An example of an assembly is enclosedwhere sheets of electrodes are separated by semi-permeable membranes.The sheets are wetted with electrolyte mixture during assembly in thiscase. An air free atomization is used to wet the film sheets duringconstruction to avoid the usual vacuum filling techniques that can harmthe nano-structures. The electrolyte easily wets through thesemi-permeable sheet into the polymer electrode, and excess fluid can becontrolled. In the case of a low voltage product with opposingpolyaniline electrodes, aqueous electrolytes can be used. In the case ofhigher voltage operation using polyaniline and Li/Al requiring highbreakdown field operation, electrolyte solutions such as PC/DME andLithium salts such as LiBF₄ are used.

The Al substrate enters the tank on the left hand side and is routed tothe bottom of the tank, and then routed back and forth over severallayers while being pulled between multiple isolated electrodes. The gapbetween upper and lower electrodes is shown here to be 9-10 mm and theelectrodes have ports for inducing flow of the aqueous solution alongthe substrate path. This fluid flow supports the film during growth,preventing contact with the electrodes and eliminating shear forces onthe nanowire structure during growth. Similarly, shear forces on thenanowire structure where the substrate travels over the guide rollerscan be eliminated by driving the rollers at line speed to avoid anyvelocity differential, and by pumping fluid through the hollowperforated rollers to maintain a fluid film between the rollers and thesubstrate. The substrate tension will be approximately 8 N and willrequire local fluid pressures of only 1.6 kPa (0.24 psi) to maintain afluid gap between the roller surfaces and the substrate. This fluidpressure is easy to obtain through entrained fluid on the driven rollersand by pumping the aqueous solution through the perforated rollers.These steps are specifically done to minimize all shear and non-uniformnormal stresses on the nanowire structure during growth.

Once the film with the nanowire structure leaves the growth tank, itwill be pulled through a drying tunnel that uses incremental mediumwavelength IR heaters and heated dry air (−40° C. dewpoint) to removethe moisture. Once dried, the nanowire structure is more robust andeasier to handle without damage. The remaining steps and handling of thesubstrates will be through use of vacuum belts and vacuum grippers. Dueto the very light weight, low tension forces and the large surfaceareas, very low levels of vacuum (<1.3 kPa, <0.2 psi) can be used forhandling purposes. These very low, uniform pressures significantlyreduce the risk of nanowire damage.

A semi-permeable membrane can be used to electrically isolate the twoelectrodes but allow ion transport (e.g. Li+ and BF₄—) between theelectrodes. Since the synthesized polyaniline formed from this method isbrush or branch like, a separator may have periodic pillars or spacersincorporated to protect the film, as shown in FIGS. 7A and 7B.

The pillars (1-2% of the total area) incorporated onto the surface ofthe separator membrane crush into the film (not less than 4 micronsthick) and establish support without sacrificing the remaining 98% or sonanostructures and their redox providing surface areas. In this way,force can be used to mount the various layers of the multilayered devicewithout crushing or reducing the available surface area of the polymernano-structured films. The lost area due to the spacer arrangement isabout 1% and the spacers can be crossed lines, round or square shapes orother shapes that provide stand-off capability. The semi-permeablespacer or separator can be made of polypropylene, Teflon, polycarbonate, cellulose based or other materials. Not to limit theapproach, but these can be pressed, etched, machined, ablated or molded.The materials can be purchased from e.g. Dupont, Celgard, LLC, etc. Thefilms are then pressed under heat to form the pillar structures, andthen expanded in the usual ways to provide the ionic transportcapability. Another method for providing the pillars or supports is byprinting dots or bumps of epoxy or other suitable material to thepermeable membrane by using micro-gravure or direct ink jet methods. Thepermeable membrane may be treated with surfactant and other additives asknown in the art.

Typical pressing conditions are 2000 psi at 180° C. and depend on themelting point of the exact material. Since the pillars only represent 1%of the area, even 25 micron pillars can be produced without losing even1 micron of film thickness. The features are formed in a roller orcalendaring technique. A second technique is the use of a saltelectrolyte/plasticizer/filler to mold a working separator with pillarsor spacers out of electrolyte containing compounds known in the art. Athird way is to provide a separate spacer device combined with asemipermeable membrane, separately or attached. Typical compounds areEC, PC, DME, PVDF, TFE and the salts are typically LiClO₄, LiBF₄ etc.

Alternating layers of cathodes and anodes are stack on top of each otherwith spacer layers that are electrically insulating but ionicallyconductive between each successive anode and cathode layers. Alignmentis such that all the anode layers extend out of one side of the stackand all the cathode layers extend out of a different side of the stack.FIG. 8B shows this alternating stack arrangement with the cathode andanode layers extending out of opposite sides of a stack. The spacerlayers are slightly wider than the anodes and cathodes and prevent theedges of the stacked sheets from coming into contact with each other.The individual anode layers are welded or mechanically staked togetherand then joined by the same means to a contactor bar. The cathode layersare similarly joined together and to a cathode contactor bar. Thisentire stacked assembly is then placed into a sealed package or casewith the ends of the contactor bars passing through the package forexternal connection to other components. This type of constructionallows for variable layer counts for different battery capacities andapplications. This type of construction also minimizes ohmic lossesduring charge and discharge. A final package is shown in FIG. 8C. Theconnector bars for the anode and cathode layers can pass through thefinal package or case on either one side each for lower power systems,or on both sides for higher power/higher current applications. Theconnector bars can be welded, riveted or staked to the battery layers.The external sections of the connector bars can be easily connected toexternal circuit components such as electrical connectors or cables.

Stacks of alternating electrode and spacer layers are produced,connecting to negative and positive posts or terminals (symmetricaldevice shown in illustration FIG. 8A) alternately. Notches or holes onalternating sheets of electrode are cut out to prevent contact to theopposite electrode/alignment pins.

In another embodiment, a low-cost supercapacitor (ultracapacitor) orbattery has extremely high specific energy, energy density, specificpower, power density, capacitance, and/or electrode surface area.

In a further embodiment, the ultracapacitor or battery consists of alayered stack of alternating positive and negative electrodes withseparation membranes between the electrodes. The positive electrodes aremade with organic polymer nanowires that are chemically synthesized ontoa base metal substrate through a linking strategy. The positiveelectrodes are grown with an electrochemical method that can beautomated inexpensively. The negative electrodes are composed of a highsurface area aluminum-lithium amalgam and are easily produced in acontinuous electrochemical process.

In yet another embodiment, the ultracapacitor requires the combinationof high energy density (high surface morphology), successful synthesison commodity metals, and successful transfer to organic electrolytes.

Final assembly of the cells preferably takes place in a dry environmentto prevent reaction of the different materials with water. Typically,the environment must be at a −40° C. dewpoint or lower. This type ofenvironment is usually generated used large desiccant air dryingsystems. By automating the assembly process and keeping the required dryair volume in the manufacturing area to a minimum, the size andoperating cost of a desiccant system can be minimized. Air drying unitscan be very large sources of power consumption due to their use of heatto regenerate the desiccant beds and due to the large blowers requiredto maintain air flow. Instead of conducting the final assembly processin a room environment where the volume is large and where people arerequired to operate, automating the process and keeping the volume to anabsolute minimum will save in equipment cost and operating costs.

The equipment is designed around a robotic assembly station withpreferably three incoming material feed lines and a secondary assemblychamber. The material feed lines consist of a set of process equipmentthat can include cutting stations, material feed drives, guidingstations and, in some cases, a material process tank that contains anon-aqueous solution. Each line can have a counterflow drying tunnel todry the incoming material and prevent moisture ingress through theincoming material.

By making the enclosures just large enough to contain the equipment andwith access panels with dry box gloves, the volume of dry air requiredcan be a fraction of that required in a traditional assembly space whilestill allowing for easy access to various points in the manufacturingequipment. The dry air enclosure includes an aluminum frame structuremade from extruded profiles with acrylic and/or polycarbonate panelsmounted within the frame. Each panel can be removed for access to theinternal machine components and also a set of dry box gloves (longsealed gloves) can be installed in any panel where frequent access orintervention may be required. The dry box gloves allow for operatoraccess while maintaining an air tight and water vapor tight seal. Theprocess equipment is preferably close enough to an enclosure panel toallow for easy operator access. This prevents the need for a personoperating within the dry air volume and reduces the moisture load on thesystem. An airlock is built onto the secondary assembly volume to allowfor the insertion and removal of material from the dry air volume. Totalenclosed volume for this system can be about 24 m³ (850 ft³). This is aquarter of the volume of a 6 m by 6 m×2.4 m (20′×20′×8′) assembly roomand there is no burden on the system to remove the moisture load fromassembly personnel.

EXAMPLES

The materials and processes of the present invention will be betterunderstood in connection with the following examples, which are intendedas an illustration only and not limiting of the scope of the invention.

Example 1 Preparation of PANi Electrode: Ni/4-APA/PANi

Polyaniline is anchored to a metal (M) surface using an anilinederivative as a linking agent (L) to create a M/L/PANi electrode. Thenickel surface is first cleaned by chemical or polishing techniques. Thesurface is then hydroxylated using three cyclic voltammetry sweepsbetween 0-0.5 V (vs. Ag/AgCl) at 20 mV/sec in a 2M aqueous KOH solutionto form Ni—OH moieties. The film is rinsed and a solution containing alinker such as 4-aminophthalic acid (4-APA, CAS#5434-21-9) is allowed toreact with the Ni—OH surface by heating in DMSO solution at 65° C. for10 min. The application of heat in a “dry” organic solvent creates acovalent bond between the Ni—OH surface and the carboxylic acid end ofthe 4-APA linker, and occurs with the elimination of water. Theresulting Ni-4-APA films are rinsed with fresh DMSO, cooled to roomtemperature and either used immediately or stored in a containercontaining a desiccant. We note that once the “organic” “hydrophobic”linker is covalently attached to the nickel surface, the coatedelectrode is stabilized and can be used in aqueous solutions to growpolyaniline fibers utilizing the NH2 group on the end opposite of the4-APA linker. Polyaniline is then grown onto the Ni/4-APA/films using atwo step procedure which involves submerging the films into an low pHaqueous solution containing polyaniline and other chemicals such ascamphor sulfonic acid, and immediately subjected the film to a 60 secondconstant current pulse, @ 1 mA/cm², that initiates growth of polyaniline“buds” onto the linker end. We note that this step appears to becritically important to producing high surface area growth. Theresulting Ni/4-APA/PANi film is then dried under low oxygen conditionsand transferred to an organic electrolyte solution. A CV of theresulting electrode is shown in FIG. 16.

Example 2 Preparation of PANi Electrode: Al/C/PANi

Polyaniline is anchored to a metal (M) surface using a carbon-based(carbon, graphite, or graphene=cgg) linking agent (L) to create aM/L/PANi electrode. The Al surface is first cleaned/etched by chemicaltechniques. The graphite (TIMREX High Surface Graphite, HSAG 300) isdeposited on the Al by orbital sander (RYOBI Model # P400). Graphitedeposition is carried out for approximately 2 seconds per side of Alwith the rate of 11000 orbits per min. Polyaniline is electropolymerizedon Al/C electrode using a 3-electrode configuration in a singlecompartment electrochemical cell with a Ni counter electrode arranged sothat it enveloped both sides of the working electrode. A standardAg/AgCl electrode is used as the reference electrode. The Ni counterelectrodes are cleaned by polishing and chemical techniques and immersedin the growth solution containing 0.45 M aniline (Sigma-Aldrich,CAS#62-53-3), 0.2 M camphor-10-sulfonic acid β (Sigma-Aldrich,CAS#5872-08-2) and pH is adjusted to 1.3 by adding H2SO4. The Al/Cworking electrode is placed in the growth solution between two Nicounter electrode plates with the distance between counter electrode andworking electrode approximately 1 cm. Constant potential method is usedto grow polyaniline films on Al/C electrodes at 0.75 V vs Ag/AgClreference (MACCOR, model # series 4300). It is noteworthy that thisgrowth voltage is 50 mV lower than with growth on platinum or other baremetal electrodes. FIGS. 17A and 17B show a typical CV in aqueous andnon-aqueous solutions, respectively. The film is then rinsed in 5%hydrazine (Sigma-Aldrich, CAS #302-01-2) solution for 5 min with orwithout vacuum. The resulting film is then dried by transferring it toan Infra Red drying chamber (300° C.) with or without N₂ flow for 5 min.The dried polyaniline film is then transferred into 0.5M LiClO₄ inacetonitrile/propylene carbonate (50/50 V/V) nonaqueous solution. SeeFIG. 5 for typical CV in nonaqueous solutions. The cyclic voltammetryexperiments are conducted in this solution on Princeton Applied ResearchPotentiostat (Model #273) with potential limits of −0.2 V and 0.8V vsAg/Ag+ standard nonaqueous reference. Longevity tests are performed onMACCOR system with charging the film to 0.8 V with 0.5 mA current rateand discharging to −0.25 V with 0.5 mA current rate. FIG. 18 shows thenearly linear nonaqueous behavior of total capacity to total aqueouscoulombic growth of the Al/C/PANi electrode.

Example 3 Negative Electrode

Due to the instability of common non-aqueous electrolyte mixtures in thevicinity of high voltage lithium based negative electrodes, a newslightly lower voltage electrode would be advantageous. Lithium aluminumalloy has an electrochemical potential 0.3 Volts less negative thanlithium metal or more importantly the decomposition voltage of propylenecarbonate electrolyte solvent. Aluminum is subject to corrosion and mustbe protected from byproducts generated or present in the electrochemicalcell. The following example is a new way to accomplish a high capacity,high current, chemically protected negative electrode for use in lithiumbased cells.

Step 1. 5052 or other suitable magnesium or other alloy Al foil, 20microns thick or so is etched in HCl 1 M solution with 5% EG in roomtemperature degassed DI water, 20 mA/cm² oxidizing current for 3 minutesto produce a high surface area substrate. In this type of electrolyticetch, the thickness of the aluminum foil remains the same even as theporosity is increased. The weight loss in this example can be about 40%.The surface area can be increased by up to a hundred times compared tothe bare aluminum foil. Electrical or ionic currents can be increasedevidenced by limited voltage drop to maintain these currents. Prior toetch, about 0.25 mA can be passed by a 1 cm² sample. After etch, as muchas 10 ma per square centimeter of substrate area (not accounting for theetched enhancement) can be passed for the same voltage drop (0.3V wasselected arbitrarily). The micro-etched features minimize cracks due tolithium based swelling and contraction. It is now practical to makealuminum foil into high current Li+ source negative electrode. The foilis then rinsed in DI water for about 5 minutes.

Step 2. When a lithium cell is charged and discharged, trace water inthe electrolyte may react on the surface of the lithium donatingelectrode causing gradual capacity loss. There is a desire to limit thisloss and to otherwise protect the surface of the aluminum foil. To thisend, zinc, tin or other easily oxidized metal can be plated over thefreshly etched aluminum foil. The plating conditions are NH₄Cl 1 M indegassed DI water with 0.1M ZnCl₂ at 4 mA/cm² rate in the amount of0.025 mAHr/cm² or so. The idea is to coat the aluminum with a metal thatwill oxidize and then to be preferentially and permanently reduced bylithium to form a lithium oxide as a protective coating. The platingshould take place immediately after the roughening etch to enhance theadhesion of the new metal. “Immediately” is defined as a short enoughtime to substantially limit Al oxide growth so that the new metal (Zn,Sn etc.) can plate successfully. The foil is then rinsed in DI water forabout 5 minutes.

Step 3. The foil is annealed and dried in an IR oven to oxidize theexposed new metal and to drive off all water. The temperature is between100 and 500 degrees C., preferably 100 to 200 in dry gas or −40 degreesdew point air to prepare it for processing in non-aqueous electrolyte.The aluminum foil is exposed to this temperature to form a fewmonolayers of metal oxide on the surface, and not more which wouldunnecessarily increase the irreversible loss of lithium upon the firstcharge. The time can be as little as 1 minute in dry air.

Step 4. The foil is now lithiated in a non-aqueous electrolyte solutioncontaining a salt of Lithium with or without a lithium counterelectrode. If the salt is LiCl complexed by AlCl₃ in PC, for example,the only byproduct of a non-lithium counter electrode setup is Cl₂ gas.The current example uses a mixture of 1:1 PC and acetonitrile, 1 molarsolution of AlCl₃ and 0.1 molar LiCl with a reducing current of 4 mA. Inthis way, as production goes on, only additional LiCl needs to be added.This process takes place in a −40 degrees C. dew point dry space. Duringthe initial lithiation, any metal (e.g. zinc) oxide will be reduced bythe lithium, and that initial lithium material will be oxidized into aprotective layer of Li₂O. Thereafter, Li+ will permeate the insolubleLi₂O and lithiate the underlying aluminum (or other Li active materiale.g. zinc, tin, etc). The foil is lithiated to a minimum amount, inorder for it to take on a −2.7 Volt electrochemical potential withrespect to an Ag/AgCl reference electrode. This amount relates to about0.25 mAHr/cm² or about 10% by aluminum atomic count. Irreversible Lilosses include both the minimum aluminum % plus the small Li₂O formingloss. The reducing current is set to 4 mA but may be lower or as high as10 mA without altering the Li+ insertion voltage that lies between −2.7and −3.0 Volts re. Ag/AgCl.

When pairing a polyaniline and aluminum foil electrode together to forman electrochemical cell, it is necessary to account for lithium ions inparticular (since most of the useful anions are relatively insoluble anddon't move far). The diagram on the left shows how the charge state of apolyaniline positive electrode determines the level of incorporatedlithium ions. The diagram on the right indicates a “plateau” of at −2.7Volts for lithiation percentages between about 10 and 50%. Therefore ifthe polyaniline is carrying a charge state of −0.2 and matched to thenegative electrode carrying a minimum level of lithiation, it will makebest utilization of lithium without over-lithiating the negativeelectrode, which can be damaging. If the negative electrode is notlithiated to the minimum value according to the graph, then some of thelithium originating during the initial charge will be lost due to theinitial irreversible capacity of the aluminum.

Energy Density

Ultracapacitor cells with polyaniline positive electrodes synthesized onnickel and Al—Li negative electrodes have been progressively optimizedusing an experimental approach. As shown in the graph below, subtlechanges in combinations of pH and dopant can result in changes toelectrical performance. Shown in FIG. 9 are films A-E that wereclassified relatively as poor, average, and promising. Film E and Frepresents promising results at a certain pH (adjusted using H₂SO₄) anddopant (CSA) level. Relative results are explained below:

-   -   Film A: Higher pH, 2× dopant level: higher pH slows growth and        added dopant grows denser PANI fibers. Film result: poor        performance.    -   Film B: Lower pH, same dopant level: lower pH speeds film growth        but is destructive to film morphology because not enough dopant        is present. Film result: poor performance.    -   Film C: Lower pH, 2× dopant: lower pH speeds film growth and        higher dopant protects film. Film Result: average film        performance.    -   Film D: Higher pH, same dopant level: higher pH slows growth.        Result: average film performance.    -   Film E and Film F: similar pH and dopant level. However, in Film        F the Li—Al electrode was altered showing improved performance        over E.

Performance variation is seen over a range of variables. The competitionbetween the dopant acid (CSA) and the general electrolytic acid (in thistest series, H₂SO₄) influences morphology and electrical performance (aswell as longevity, not shown). Other parameters such as synthesisvoltage, temperature, and transfer conditions are shown to be important.

The performance characteristics of these synthesized films are based onthe rinsed and dried microbalance weights and micrometer measuredthickness. The thickness of the above reported films is between 10 and30 microns, such as about 11 microns, and the mass is about 0.0009grams/cm². These values of weights and thickness are typical for thefabrication and testing procedure used to evaluate growth variables.

The capacitance measured on discharge curve (F) on FIG. 9 above is about0.91 F/cm², which corresponds to over 1000 F/g of polyaniline. Thisvalue compares favorably with several electrolytically grown polyanilinenanowire demonstrations on platinum.

The electrical and physical data given here is used in the ComputationModel of Specific Energy, Energy Density, Specific Power and Powerpresented below. Among other parameters, film thickness, energy densityper square centimeter, and mass are entered into the model.

RAW Data at Fast Discharge Rate—can be used to compute specific powerand power density for 30 s at 80% DOD.

A similar constant current discharge test, performed this time at 2.5mA/cm², may be used to calculate the “maximum” power deliverable for 30seconds commencing with 80% DOD.

The 30 second interval commencing with 80% DOD (5225-5250 seconds)indicates a power during that time of 7 mw/cm².

Preliminary Measurements of Cycle Life

Accelerated lifetime experiments on the polyaniline electrode using aplatinum substrate show no material degradation after 25,000charge-discharge cycles. Below, two overlaid CV curves demonstratelittle degradation after 5000 and 25000 operating cycles on theaforementioned platinum electrode test.

A similar accelerated test on a polyaniline electrode using a modifiedbase metal substrate has been conducted. This CV test, run at a 4 mV/secsweep rate, shows little degradation through 850 cycles. In FIG. 12, thelines compare the 50^(th) and 850^(th) cycle. Note that the voltage inthis test is shown against an Ag/AgCl reference.

The following FIG. 14 describes performance of a half cell arrangementof polyaniline electrochemically synthesized onto graphite scrubbedAluminum 1145. The sweep rates were roughly equivalent to 15 mv/sec. for250 cycles, and then one cycle at an equivalent of 4 mv/sec sweep rate.This half cell test was continued for over 4000 cycles as shown here.Since peak currents are proportion to capacity, they are used here tomonitor longevity of the film at the two charge and discharge rates.Over the course of this test, the peak currents declined by only 21%. Werecognize that, a shift of performance occurred near the center of thetest period, and this may be attributed to a change in the roomtemperature of the test lab over the same period. Performance hasincreased to 0.8 mAhr/cm², which, if discharged against a suitablenegative electrode such as lithiated aluminum resulting in a full cellaverage voltage of 3.7 V. Etched, lithiated aluminum 5052 are preferred.Initial cycle tests (over 600) have been measured in half cell with asilver wire pseudo reference electrode. Initial measured values of 1mAhr/cm² capacity exceed that of the positive electrode, and appearsufficient to support our full cell voltage assumptions.

While there has been illustrated and described what is at presentconsidered to be the preferred embodiment of the present invention, itwill be understood by those skilled in the art that various changes andmodifications may be made and equivalents may be substituted forelements thereof without departing from the true scope of the invention.Therefore, it is intended that this invention not be limited to theparticular embodiment disclosed, but that the invention will include allembodiments falling within the scope of the appended claims.

What is claimed is:
 1. A method for making a lithiated electrodecomprising lithiating an aluminum electrode wherein a reducing currentis applied in a moisture free organic electrolyte solution comprising alithium salt.
 2. The method of claim 1, wherein the aluminum electrodecomprises a magnesium containing aluminum alloy.
 3. The method of claim1, wherein the aluminum alloy comprises between 1 and 20 atom percentmagnesium.
 4. The method of claim 1, wherein the aluminum alloycomprises at least 3 atom percent magnesium.
 5. The method of claim 1,wherein the reducing current is about 5 ma/cm².
 6. The method of claim1, wherein the lithium salt is selected from the group consisting ofLiSO₄, LiBF₄ and LiClO₄.
 7. The method of claim 1, wherein the lithiumsalt is maintained in a concentration of at least about 0.5M.
 8. Themethod of claim 1, wherein the lithium salt is maintained in aconcentration of at least about 1.0M.
 9. The method of claim 1, whereinthe organic electrolyte solution comprises propylene carbonate anddimethoxyethane (PC/DME).
 10. The method of claim 1, wherein lithium isadded to the aluminum electrode in an amount of about 5 and 30 atompercent.
 11. The method of claim 1, wherein the moisture conditions areless than −40 degrees dew point air.
 12. The method of claim 1, whereinthe aluminum electrode is electrochemically etched prior to lithiation.13. The method of claim 1, wherein the electrochemical etching isachieved by adding a 1 M HCl, 5% ethylene glycol solution at roomtemperature with an oxidizing current.
 14. The method of claim 1,wherein the oxidizing current is at least 0.02 A/cm3.